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Speed bump question - newton's laws

  1. Mar 22, 2009 #1
    1.
    You're driving down the road at 8 m/s and go over a speed bump. When you go over the bump, you feel lifted from your seat. Explain why.


    I assumed it was because of inertia, but I'm not sure.

    You weigh 700 N. If it is approximated that the speed bump is shaped like an arc of a circle, with radius of 10 m, find the magnitude of force the seats exerts on you as you go over the speed bump.

    If F = mv^2/r, then would you just plug everything in directly?
     
  2. jcsd
  3. Mar 22, 2009 #2

    Delphi51

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    The seat normally pushes upward on you with 700 N (because you push down on it with 700 N weight). While in circular motion, though, you experience a centrifugal force upward that reduces the 700 N.
     
  4. Mar 22, 2009 #3
    So while in circular motion, you aren't pushing down on the seat with 700 N so you are lifted up?
     
  5. Mar 22, 2009 #4

    Delphi51

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    It is unlikely you will float up off the seat - that would take a terrific speed - but the force pressing you against the springs of the seat will be reduced so the spring compression will be less and you will go up a little bit.
     
  6. Mar 22, 2009 #5
    But would the seat still exert 700 N upward? I mean, would I just plug in the numbers into the equation for the second part?
     
  7. Mar 22, 2009 #6

    Delphi51

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    700 - mv^2/r
     
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